1. Field of the Invention
The present invention relates to a method and apparatus for patching a hole and more particularly, for patching a hole in an instrument console panel. This method and apparatus provides a patch that is flush with both the inner surface and the outer surface of the panel.
2. Description of Prior Art
Welding as a method of patching a hole in a panel which houses highly sensitive electronics equipment can jeopardize the components and the operation of the circuitry. Welding or the use of adhesives to secure the patch in a hole may not be acceptable methods in the delicate environment of electronics equipment. A technique to patch a hole which does not produce excessive fumes, create undue heat, utilize a high current, or induce a strong magnetic field would be highly useful under such restrictive conditions.
U.S. Pat. No. 2,011,484 issued Aug. 13, 1935 to Hal W. Harman describes a method for repairing cracks in castings. A hole is drilled and tapped at one end of the crack and filled with a bolt. With the bolt screwed tightly into the hole, the head is sheared off flush with the casting. Another hole is drilled adjacent to and overlapping the previously filled hole. This hole is also tapped and filled with a bolt. The head of the bolt is again sheared off flush with the casting. This step is repeated along the crack, each hole adjacent to and overlapping the previously filled hole until the crack is filled. U.S. Pat. No. 2,121,692 issued Jun. 21, 1935 to Newell Hays discloses a method for closing cracks in a casting by drilling spaced holes in the casting along the line of the crack. The face of the casting is channeled so the holes are disposed along the center of the channel. The holes are tapped and screws are inserted into the holes. The heads of the screws are peened over to completely fill the channel. U.S. Pat. No. 2,361,701 issued Oct. 31, 1944 to Charles Michaels teaches a method for repairing a crack in a casting with contacting screws. A series of adjacent, angled holes are drilled, tapped and filled with contacting screws having heads projecting above the surface of the casting. The screw heads are then welded to fill the crack with metal. U.S. Pat. No. 2,998,645 issued Sep. 5, 1961 to David Diperstein demonstrates a method for repairing a crack in metal parts. A series of overlapping holes are drilled along the crack in the metal. Each hole is tapped to accommodate a bolt having a weakened point intermediate its length. The bolt is threaded into the hole and torque is applied to the bolt until its shears at the weakened point. This method requires a series of locks located across the crack to reduce the risk of widening of the crack.
U.S. Pat. No. 4,599,781 issued Jul. 15, 1986 to David Diperstein teaches a further a method of repairing cracks in thin metal parts, specifically 1/8 inch or less cast iron or 1/4 inch or less aluminum. The steps of the method are about the same as in his earlier U.S. Pat. No. 2,998,645 just discussed and involve providing a series of holes along the crack, tapping each hole with a thread to mate with a plug, and filling the holes with the plugs by threading the plugs into the holes and applying torque to the plugs until the force of the torque applied exceeds the strength of the plugs whereby a portion of the plug snaps off beyond the surface of the crack. Precise dimensions and plug threading are mandatory for the method to work with thin metal plate. U.S. Pat. No. 4,845,828 issued Jul. 11, 1989 to Gary J. Reed illustrates yet another method of repairing a crack or break in a metal casting. A repair in a crack is performed in a manner whereby a series of holes are drilled, tapped, and plugged with a plug that breaks off at a "break-off" groove when a certain torque is reached. A particularly configured metal bar lock is required to hold the crack closed to prevent the crack from spreading. The metal bar lock fits in a recess in the casting. The recess is carved to conform to the peripheral contour of the bar lock except where semi-circular notches are located in the metal bar lock which correspond to semi-circular notches in the casting. When the metal bar lock is inserted into the recess, the notches in the casting line up with those in the metal bar lock for receiving a securing plug which is threaded thereinto until the torque applied exceeds the strength of the plug whereby the plug breaks off at the break-off point.